The invention relates generally to a method and apparatus for applying energy to shrink a hollow anatomical structure, such as a fallopian tube or a vein, including but not limited to, superficial and perforator veins, hemorrhoids, and esophageal varices. In some particular aspects, the invention relates to a method for compressing an anatomical structure prior to the application of energy and apparatus including an electrode device having multiple leads for applying energy to the compressed structure to cause it to durably assume its compressed form.
The human venous system of the lower limbs consists essentially of the superficial venous system and the deep venous system with perforating veins connecting the two systems. The superficial system includes the long or great saphenous vein and the short saphenous vein. The deep venous system includes the anterior and posterior tibial veins which unite to form the popliteal vein, which in turn becomes the femoral vein when joined by the short saphenous vein.
The venous system contains numerous one-way valves for directing blood flow back to the heart such as those valves 20 located in the vein 22 shown in FIG. 1. The arrow leading out the top of the vein represents the antegrade flow of blood back to the heart. Venous valves are usually bicuspid valves, with each cusp 24 forming a sack or reservoir 26 for blood which, under retrograde blood pressure, forces the free surfaces of the cusps together to prevent retrograde flow of the blood and allows only antegrade blood flow to the heart. Competent venous valves prevent retrograde flow as blood is pushed forward through the vein lumen and back to the heart. When an incompetent valve 28 is in the flow path, the valve is unable to close because the cusps do not form a proper seal and retrograde flow of the blood cannot be stopped. When a venous valve fails, increased strain and pressure occur within the lower venous sections and overlying tissues, sometimes leading to additional valvular failure. Incompetent valves may result from the stretching of dilated veins. As the valves fail, increased pressure is imposed on the lower veins and the lower valves of the vein, which in turn exacerbates the failure of these lower valves. A cross-sectional perspective view of a dilated vein with an incompetent valve 28 taken along lines 2--2 of FIG. 1 is illustrated in FIG. 2. The valve cusps 24 can experience some separation at the commissure due to the thinning and stretching of the vein wall at the cusps. Two venous conditions which often result from valve failure are varicose veins and more symptomatic chronic venous insufficiency.
The varicose vein condition includes dilation and tortuosity of the superficial veins of the lower limbs, resulting in unsightly discoloration, pain, swelling, and possibly ulceration. Varicose veins often involve incompetence of one or more venous valves, which allow reflux of blood within the superficial system. This can also worsen deep venous reflux and perforator reflux. Current treatments of vein insufficiency include surgical procedures such as vein stripping, ligation, and occasionally, vein-segment transplant.
Chronic venous insufficiency involves an aggravated condition of varicose veins which may be caused by degenerative weakness in the vein valve segment, or by hydrodynamic forces acting on the tissues of the body, such as the legs, ankles, and feet. As the valves in the veins fail, the hydrostatic pressure increases on the next venous valves down, causing those veins to dilate. As this continues, more venous valves will eventually fail. As they fail, the effective height of the column of blood above the feet and ankles grows, and the weight and hydrostatic pressure exerted on the tissues of the ankle and foot increases. When the weight of that column reaches a critical point as a result of the valve failures, ulcerations of the ankle begin to form, which start deep and eventually come to the surface. These ulcerations do not heal easily because of poor venous circulation due to valvular incompetence in the deep venous system and other vein systems.
Other related venous conditions include dilated hemorrhoids and esophageal varices. Pressure and dilation of the hemorrhoid venous plexus may cause internal hemorrhoids to dilate and/or prolapse and be forced through the anal opening. If a hemorrhoid remains prolapsed, considerable discomfort, including itching and bleeding, may result. The venous return from these prolapsed hemorrhoids becomes obstructed by the anal sphincters, which gives rise to a strangulated hemorrhoid. Thromboses result where the blood within the prolapsed vein becomes clotted. This extremely painful condition can cause edema and inflammation.
Varicose veins called esophageal varices can form in the venous system with submucosa of the lower esophagus, and bleeding can occur from the dilated veins. Bleeding or hemorrhaging may result from esophageal varices, which can be difficult to stop and, if untreated, could develop into a life threatening condition. Such varices erode easily, and lead to a massive gastrointestinal hemorrhage.
Ligation of a fallopian tube (tubal ligation) for sterilization or other purposes is typically performed by laparoscopy. A doctor severs the fallopian tube or tubes and ties the ends. External cauterization or clamps may also be used. General or regional anesthetic must be used. All of the above are performed from outside the fallopian tube.
Hemorrhoids and esophageal varices may be alleviated by intra-luminal ligation. As used herein, "ligation" or "intra-luminal ligation" comprises the occlusion, collapse, or closure of a lumen or hollow anatomical structure by the application of energy from within the lumen or structure. As used herein, "ligation" or "intra-luminal ligation" includes electro-ligation. In the case of fallopian tube ligation, it would be desirable to perform the ligation from within the fallopian tube itself (intra-fallopian tube) to avoid the trauma associated with external methods.
Ligation involves the cauterization or coagulation of a lumen using energy, such as that applied through an electrode device. An electrode device is introduced into the lumen and positioned so that it contacts the lumen wall. Once properly positioned, RF energy is applied to the wall by the electrode device thereby causing the wall to shrink in cross-sectional diameter. In the case of a vein, a reduction in cross-sectional diameter of the vein, as for example from 5 mm (0.2 in) to 1 mm (0.04 in), significantly reduces the flow of blood through a lumen and results in an effective occlusion. Although not required for effective occlusion or ligation, the vein wall may completely collapse thereby resulting in a full-lumen obstruction that blocks the flow of blood through the vein. Likewise, a fallopian tube may collapse sufficiently to effect a sterilization of the patient.
One apparatus for performing ligation includes a tubular shaft having an electrode device attached at the distal tip. Running through the shaft, from the distal end to the proximal end, are electrical leads. At the proximal end of the shaft, the leads terminate at an electrical connector, while at the distal end of the shaft the leads are connected to the electrode device. The electrical connector provides the interface between the leads and a power source, typically an RF generator. The RF generator operates under the guidance of a control device, usually a microprocessor.
The ligation apparatus may be operated in either a monopolar or bipolar configuration. In the monopolar configuration, the electrode device consists of an electrode that is either positively or negatively charged. A return path for the current passing through the electrode is provided externally from the body, as for example by placing the patient in physical contact with a large low-impedance pad. The current flows between the ligation device and low impedance pad through the patient. In a bipolar configuration, the electrode device consists of a pair of electrodes having different potentials (such as a pair of oppositely-charged electrodes) of approximately equal size, separated from each other, such as by a dielectric material or by a spatial relationship. Accordingly, in the bipolar mode, the return path for current is provided by an electrode or electrodes of the electrode device itself. The current flows from one electrode, through the tissue, and returns by way of the another electrode.
To protect against tissue damage, i.e., charring, due to cauterization caused by overheating, a temperature sensing device is typically attached to the electrode device, although it may be located elsewhere. The temperature sensing device may be a thermocouple that monitors the temperature of the venous tissue. The thermocouple interfaces with the RF generator and the controller through the shaft and provides electrical signals to the controller which monitors the temperature and adjusts the energy applied to the tissue through the electrode device accordingly.
The overall effectiveness of a ligation apparatus is largely dependent on the electrode device contained within the apparatus. Monopolar and bipolar electrode devices that comprise solid devices having a fixed shape and size can limit the effectiveness of the ligating apparatus for several reasons. Firstly, a fixed-size electrode device typically contacts the vein wall at only one point or a limited arc on the circumference or inner diameter of the vein wall. As a result, the application of RF energy is highly concentrated within the contacting venous tissue, while the flow of RF current through the remainder of the venous tissue is disproportionately weak. Accordingly, the regions of the vein wall near the area of contact collapse at a faster rate than other regions of the vein wall, resulting in non-uniform shrinkage of the vein lumen. Furthermore, the overall strength of the occlusion may be inadequate and the lumen may eventually reopen. To avoid an inadequate occlusion, RF energy must be applied for an extended period of time so that the current flows through the tissue, including through the tissue not in contact with the electrode, generating thermal energy and causing the tissue to shrink sufficiently. Extended applications of energy have a greater possibility of increasing the temperature of the blood to an unacceptable level and may result in a significant amount of heat-induced coagulum forming on the electrode and in the vein which is not desirable. Furthermore, it is possible for the undesirable coagulum to form when utilizing an expandable electrode as well. This problem can be prevented by exsanguination of the vein prior to the treatment, as well as through the use of temperature-regulated power delivery. As used herein, "exsanguination" comprises the removal of all or some significant portion of blood in a particular area.
Secondly, the effectiveness of a ligating apparatus having a fixed-size electrode device is limited to certain sized veins. An attempt to ligate a vein having a diameter that is substantially greater than the fixed-size electrode device can result in not only non-uniform heating of the vein wall as just described, but also insufficient shrinkage of the vein diameter. The greater the diameter of the vein relative to the diameter of the electrode device, the weaker the energy applied to the vein wall at points distant from the point of electrode contact. Also, larger diameter veins must shrink a larger percentage for effective occlusion to occur. Accordingly, the vein wall is likely to not completely collapse prior to the venous tissue becoming over-cauterized at the point of electrode contact. While coagulation as such may initially occlude the vein, such occlusion may only be temporary in that the coagulated blood may eventually dissolve recanalizing the vein. One solution for this inadequacy is an apparatus having interchangeable electrode devices with various diameters. Another solution is to have a set of catheters having different sizes so that one with the correct size for the diameter of the target vein will be at hand when needed. Such solutions, however, are both economically inefficient and can be tedious to use. It is desirable to use a single catheter device that is usable with a large range of sizes of lumina.
A technique of reducing the diameter of the lumen of a vein at least close to the final desired diameter before applying energy to the vein has been found to aid in the efficiency of these types of procedures. The pre-reduction in vein diameter assists in pre-shaping the vein to be molded into a ligated state. The compression also exsanguinates the vein and forces blood away from the treatment site, thus preventing coagulation. One valuable technique employed is that of compressing the vein contained within a limb by applying external hydraulic pressure, via a pressure tourniquet, to the limb. Unfortunately there are some areas of the body to which a pressure tourniquet cannot be applied, such as the sapheno-femoral junction, which is above the thigh proximate the groin area. Furthermore, there are sites where a pressure tourniquet may be ineffective such as: the popliteal junction and other areas around the knee; and the ankle area (typically the posterior arch vein and some of the lower cockett perforators).
There exists a technique referred to as tumescent anesthesia that has been used in connection with liposuction procedures. The word "tumescent" means swollen or firm. This technique is accomplished by subcutaneously delivering into target fatty tissue a large volume of saline solution containing diluted Lidocaine and Epinephrine (adrenaline), a vasoconstrictive drug. The injected area then becomes locally anesthetized, and the adrenaline temporarily constricts the capillaries and other blood vessels. The tumescence-inducing fluid, or "tumescent fluid" is injected under pressure which causes the target fatty tissue to become swollen and firm. The tumescent fluid is typically pumped into the pocket of fat in order to numb the area, loosen the fat, and constrict the blood vessels to minimize bleeding or bruising in a liposuction procedure. The anesthetic and other agents in the tumescent solution should be allowed sufficient time to diffuse and take full effect throughout the target tissue. After surgery, patients may leave without assistance, and often return to their regular routine within several days. With the tumescent technique, postoperative discomfort is significantly reduced. The local anesthesia often remains in the treated tissue for 16 hours after surgery. Employing a technique of utilizing tumescent anesthesia in conjunction with ligation or radial lumen shrinkage less than ligation may provide benefits.
Although described above in terms of a vein, the concepts are generally applicable to other hollow anatomical structures in the body as well. The above description has been generally confined to veins in consideration of avoiding unnecessary repetition.
Hence those skilled in the art have recognized a need for an improved method and apparatus that can be used on areas of the body to shrink and ligate hollow anatomical structures. A need has also been recognized for an improved method and apparatus to pre-compress and exsanguinate a hollow anatomical structure while providing anesthetic and insulation benefits during the radial shrinkage of the hollow anatomical structure. The invention fulfills these needs and others.